Here, t is the ultrasonic travel time of each path, v is the ultrasonic velocity and u is the wind velocity.
Previous systems using the time-sharing method were not affected by the temperature of the wind when applying Eqs. (2) and (3) and this removed the v factor which is sensitive to temperature [8,9]. However, in this proposed system, the transit time of the ultra- sonic signals is not measured when there is no wind. Therefore, this study calibrates when the wind velocity is calculated with a temperature sensor. Fig. 2 is the result of calculating the change of delay time by temperature in the designed system. The variation is small in the low wind velocity. However, the change is huge in the case of high wind velocity, and hence compensation is required